The SUMO E3 ligase, AtSIZ1, regulates flowering by controlling a salicylic acid-mediated floral promotion pathway and through affects on FLC chromatin structure.
The SUMO E3 ligase, AtSIZ1, regulates flowering by controlling a salicylic acid-mediated floral promotion pathway and through affects on FLC chromatin structure.
复制标题
DOI：
10.1111/j.1365-313x.2007.03359.x
复制
发表时间：
2008-02
期刊：
影响因子：
--
通讯作者：
Hasegawa PM
中科院分区：
文献类型：
--
作者：
Jin JB;Jin YH;Lee J;Miura K;Yoo CY;Kim WY;Van Oosten M;Hyun Y;Somers DE;Lee I;Yun DJ;Bressan RA;Hasegawa PM
siz 1功能丧失突变导致短日照下早开花。siz 1植物具有升高的水杨酸（SA）水平，其通过表达细菌水杨酸羟化酶nahG而恢复至野生型水平。siz 1的早期开花受到抑制表达nahG，表明SIZ 1抑制开花的过渡主要是通过抑制SA依赖的开花促进信号在短日照下。以前的结果表明，外源SA处理不抑制自主途径突变体的晚开花。然而，siz 1突变加速开花时间的自主途径突变体，luminidependens，通过减少表达的FLOWERLOCUS C（FLC），花的阻遏物。这一结果表明，SIZ 1促进FLC的表达，可能是通过SA-独立的途径。有证据表明，SIZ 1是所需的FLC的表达在晚开花的FRIGIDA背景的充分激活。有趣的是，增加FLC的表达和自主途径突变体，开花位点d（fld），开花晚，不抑制siz 1，这表明SIZ 1通过抑制FLD促进FLC的表达。与此相一致，SIZ 1促进FLD的类小泛素化，这可以通过FLD中三个预测的类小泛素化基序（即FLDK 3R）中的突变来抑制。此外，在fld原生质体中FLDK 3R的表达与FLD的表达相比强烈降低了FLC转录，并且这种影响与FLC染色质中组蛋白4的乙酰化降低有关。两者合计，结果表明，SIZ 1是一种花阻遏物，不仅抑制SA依赖性途径，而且还通过SUMO化抑制FLD活性来促进FLC表达，这是FRIGIDA背景下FLC完全表达所必需的。
Loss-of-function siz1 mutations caused early flowering under short days. siz1 plants have elevated salicylic acid (SA) levels, which are restored to wild-type levels by expressing nahG, bacterial salicylate hydroxylase. The early flowering of siz1 was suppressed by expressing nahG, indicating that SIZ1 represses the transition to flowering mainly through suppressing SA-dependent floral promotion signaling under short days. Previous results have shown that exogenous SA treatment does not suppress late flowering of autonomous pathway mutants. However, the siz1 mutation accelerated flowering time of an autonomous pathway mutant, luminidependens, by reducing the expression of FLOWERING LOCUS C (FLC), a floral repressor. This result suggests that SIZ1 promotes FLC expression, possibly through an SA-independent pathway. Evidence indicates that SIZ1 is required for the full activation of FLC expression in the late-flowering FRIGIDA background. Interestingly, increased FLC expression and late flowering of an autonomous pathway mutant, flowering locus d (fld), was not suppressed by siz1, suggesting that SIZ1 promotes FLC expression by repressing FLD. Consistent with this, SIZ1 facilitates sumoylation of FLD that can be suppressed by mutations in three predicted sumoylation motifs in FLD (i.e. FLDK3R). Furthermore, expression of FLDK3R in fld protoplasts strongly reduced FLC transcription compared with expression of FLD, and this affect was linked to reduced acetylation of histone 4 in FLC chromatin. Taken together, the results suggest that SIZ1 is a floral repressor that not only represses the SA-dependent pathway, but also promotes FLC expression by repressing FLD activity through sumoylation, which is required for full FLC expression in a FRIGIDA background.